My plumber backed out on us and have not been able to get any call backs from any others, so looks like we are on our own. I am trying to plan my under slab stuff so we can pour. The drain seems pretty straight forward, but the venting has me confused. See plumbing layout below. [b]Note we will have two sinks in the master bath, plan shows one. Also we have a one room loft directly above both bathrooms, so hopefully can vent around that room?[/b] Questions: 1. What fixtures should/can I combine to vent together? 2. Do all vent pipes need to connect under slab close the all p-traps then come up a wall? thanks for any advice and help [img]https://cimg7.ibsrv.net/gimg/www.doityourselft.com-vbulletin/2000x1504/05ac5aca_1982_4bfb_8867_614f99815dd1_5bc420fc55c2178960304bf35b5c559bb76fb11d.jpeg[/img] .

About 25 years or so ago I had underground sprinklers installed in my house and since the contractor said he had to call a plumber to install the required ball valve and backflow preventer shown in my pictures(I think that’s what you call this fitting) I offered to install these fittings myself and all worked fine for about 5 years and the contractor will come every Fall to blow the system dry. Then City Hall banned the use of these sprinklers for water conservation and I stopped using the sprinklers since. However every Fall I have to cut the water to outside two hose bibs I have to prevent water freezing. In the front hose bib shown in the picture here, I shut the ball valve from inside the house and then I open the drain valve inside the house + the one outside and let the water drain completely. The next day I shut off the exterior hose bib to prevent anything going into it but after a few days when I open that hose bib there is lots of water, with some pressure, coming out again. The picture you see of the exterior hose bib I had this valve closed last week and today when I took the picture I opened the valve and water splatter all over the wall and floor and its visible on the picture. Then the water will stop coming out and eventually will stop. I will estimate the water coming out is about 1/2 gallon. When the ball valve is shut and the sprinklers have been dead for years where all this water come from? [img]https://cimg4.ibsrv.net/gimg/www.doityourselft.com-vbulletin/979x734/2_interior_piping_188432403aed92d218549fdb82cac6cb6c4d1a2a.jpg[/img] [img]https://cimg7.ibsrv.net/gimg/www.doityourselft.com-vbulletin/979x734/3_interior_piping_3a99a3d31a0186e4d003d33e53a08a993452a628.jpg[/img] [img]https://cimg1.ibsrv.net/gimg/www.doityourselft.com-vbulletin/734x979/5_exterior_piping_69f3a8584c93eaf549925c32d5acfe78c0ca0f16.jpg[/img]